The present invention relates to a wire conductor for a wiring harness usable, for example, in electrical connections between electric or electronic appliances or inside such appliances, or in a wiring harness of an automobile.
For example, in electrical connections between electric or electronic appliances or inside such appliances, or in a wiring harness for an automobile, there is used a wire conductor 1 for the harness, comprising (1) a stranded wire 5 obtained by twisting strands 3 around a core wire 2 and (2) an insulator cord (e.g. a polyvinyl chloride) or the like covering the stranded wire 5, such as shown in FIG. 2(a) or 2(b) [in FIG. 2(b), the insulator cord is not shown for simplicity]. As mentioned above, the wire conductor 1 for the harness is produced by twisting the strands 3 around the core wire 2; therefore, the harness has flexibility and, compared to a single strand having the same cross-sectional area used to achieve the same conductivity, can be easily bent in wiring or the like without causing disconnection. Therefore, the wire conductor 1 for the harness is suitably used when many wirings are needed in a small space as in the case of (1) wiring in the control circuit of electric or electronic appliances or automobiles or (2) electrical connection between various appliances. Annealed copper has been mainly used as the conducting wires used in wire conductors for the harness.
In recent years, control circuits of increased number have come to be required in electric or electronic appliances and automobiles because the appliances and automobiles exhibit higher performance; control circuits of smaller size have come to be required in the above appliances and automobiles because the appliances and automobiles have become smaller in size; and also, because, smaller weights have come to be required for automobiles from the standpoint of energy savings. For these reasons, it is desirable that the wire conductor for the harness is made lighter, and can be produced in a smaller diameter and bent more easily so as to allow wiring in a smaller space. Conducting wires composed of annealed copper have insufficient strength although they have more than sufficient conductivity. Therefore, in order to produce a wire conductor for a harness having appropriate strength by using such conductive wires, it has been inevitable that the wire conductor for the harness have the same diameter as that employed in conventional wire conductors for the harness.
Hence, in order to produce a wire conductor for a harness of lighter weight and smaller diameter, for example, JP-B-60-30043 and JP-A-5-266719 disclose a wire conductor for a harness obtained by twisting strands composed of a copper alloy such as Sn--Cu, Cr--Cu or the like. Also, JP-A-03-184210 discloses a wire conductor for a harness obtained by twisting strands whose center is composed of an alloy containing steel as a main component and whose periphery is composed of copper or a copper alloy. Also, JP-A-08-124420 discloses a wire conductor for harness obtained by twisting reinforced fine copper wires containing finely dispersed reinforcing aluminum. Further, JP-A-60-150502 mentions on a wire conductor obtained by twisting strands having a center composed of a copper alloy such as beryllium copper or the like and whose periphery is composed of pure copper such as electrolytic copper, oxygen-free copper, deoxidized copper or the like.
These wire conductors, however, have had problems. The wire conductor using a Sn--Cu alloy has insufficient conductivity and strength and is difficult to use if it has a cross-sectional area of 0.2 mm.sup.2 or less. The Cr--Cu alloy does not have sufficient tensile strength and ductility and accordingly has insufficient strength; moreover, when, as shown in FIG. 3, the end of a wire conductor 1 is held by a terminal 6 or the like, in order to connect the end of the wire conductor 1 with the terminal 6 or the like, the contact between the wire conductor 1 and the terminal 6 is bad because the Cr--Cu alloy has high hardness and low flexibility. The wire conductor whose center is composed of an alloy containing steel as a main component has a sufficient strength; however, since substantially no electricity flows in the steel portion of large resistance, no desired conductivity is obtained when the wire conductor is produced in a small diameter.
The wire conductor using reinforced fine copper wires containing finely dispersed reinforcing aluminum, and the wire conductor obtained by twisting strands whose center is composed of a copper alloy and whose periphery is composed of pure copper, are desired to have, when used in automobiles, a higher strength than when used as a wire conductor for a wiring harness, to achieve a lighter weight and a lower fuel consumption.